Regulation of alternating generators



(No Model.) 3 SheetsvSheet 1.

P. P. IDE. REGULATION OF ALTERNATING GENERATORS.

Patented Now-12,- 1895.

MIBREW BEHAHAM.PHOTO-UTHQWASHINEYON 0c.

(No Model.) 7 3 Sheets-Shet 2. F. P. IDE. REGULATION OF ALTERNATINGGENERATORS.

No. 549,644. Patented Nov. 12, 1895.

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F. P. IDE. REGULATION OF ALTERNATING GENERATORS.

No. 549,644. Patented Nov. 12, 1895.

jalvzcvlsxfak NDREW BORMMM. PHOTO-m1").WASNINGTDN.B Qv

UNITED STATES PATENT OFFICE.

FRANCIS P. IDE, OF EAU CLAIRE, \VISCONSIN.

REGULATION OF ALTERNATING GENERATORS.

SPECIFICATION forming part of Letters Patent No. 549,644, dated November12, 1895.

Application filed April 6, 1895. Serial No. 544,753. (No model.)

T0 whmn it may concern.-

Be it known that I, FRANCIS P. IDE, a citizen of the United States,residing at Eau Claire, in the county of Eau Claire and State oflVisconsin, have invented a certain new and useful Improvement in theRegulation of Alternating-Current Generators, (Case No. 1,) of which thefollowing is a full, clear, concise, and exact description, referencebeing had to the accompanying drawings, forming a part of thisspecification.

My invention relates to the regulation of alternating-currentgenerators, and its object is to improve the construction of thealternatingcurrent apparatus whereby more nearly ideal regulation may beobtained than has been possible heretofore.

Alternating-current dynamos have been constructed having a number ofpolar projections alternating in polarity, in front of which thearmature is adapted to rotate, the fieldcoils being supplied by acontinuous current from a separate machine or exciter. In machines asthus constructed it is impossible to maintain a constant potential atthe terminals of the alternating-current machine under varying loads,for although the field is maintained constant the increased armaturereaction, due to the flow of an increased current as the output of themachine is increased, cuts down the effective field strength, this, withother causes, reducing the potential of the machine. It has beenproposed to compound machines as thus constructed to automatically varythe field strength with the change of current-output, thus compensatingfor the increased armature reaction. To accomplish this result, arectifier has been interposed in the circuit of the armature adapted tochange the alternating current induced in the armature into a direct orpulsating current, the current thus rectified being passed throughfield-coils provided upon a few or all of the field-poles,the currentbeing then transformed back into an alternating current and conducted tothe line. The coils thus trave'rsed by the rectified current are inseries with the load and act as the series winding of a compound-woundmachine to increase the field as the current-output of the machine isincreased. Instead of providing coils for the main field adapted to betraversed by the rectified current, additional field-coils may beprovided upon the exciter, through which the rectified current isadapted to be passed, so that as the output of the generator isincreased the field of the eXciter is correspond ingly increased,thus'increasing the potential of the eXcit-er and causing an increasedcurrent to flow through the field-coils of the generator. By providingthe field-coils for the rectified current upon the exciter instead ofupon the generator itself the apparatus may be greatly simplified, sinceit is necessary to provide only one or two field-coils upon the exciter,whereas by the former method it was necessary for best results toprovide a coil for the rectified current upon each of the severalpole-pieces of the generator, usually ten or more in number. As theseries coil of the exciter consists of but few turns and as the ironwhich it magnetizes is a small mass, the tendency to spark at therectifying-co1n mutator is reduced proportionately, and it is possibleto rectify the entire current of the generator without the slightestsparking and without the use of shunts either around the rectifier oraround the series coil to act as a discharge-path. As the rectifiedcurrent is pulsatory in character, varying from zero to a maximum ateach pulsation, the rectified current meets considerable inductiveresistance in passing through the field-coils, and when the rectifiedcurrent is passed through a few coils upon the eXciter the field-magnetof which may be made of laminated sheets or bundles of iron wire, theinductive resistance is a great deal less than that encountered by therectified current in passing through the several coils on the generator.As the energizing action of the rectified current is applied to theeXciter-field, such action is many times multiplied through theresulting current-output of the exciter. The magnetizing force of thegenerator-field is multiplied in like proportion, and there is thereforean abundance of magnetizing force to produce any desired result, asensitive regulation being thus permitted.

A further advantage arising from the employment of the coils of therectified current upon the exciter is that a special form of exoiter,which forms a feature of my invention, may be employed wherebypractically percatin g that for equal increments of magnetizing forcethe potential of the exciter increases at a diminishing rate. If thecurve of exciter potential for ideal regulation be-plotted, however, itwill be found that the curve is convex to the axis of the-abscissas,lying below the former curve for low magnetizing force and rising-aboveit as the magnetizing force increases, thus indicating that for smallloads the exciter potential is greater than is necessary for idealregulation, while at higher loads the exciter potential is less thanthat necessary for ideal regulation.

I have been able by means "of any invention'to cut down the exciterpotential for small loads and to increase the potential for large loads,whereby the potential of the exciter is caused to follow the curvefor-ideal regulation within such narrow limits as to make regulationideal for all practical purposes. To accomplish this, Iprovide amagnetic circuit adapted to act as a shunt about the armature of theexciter, whereby for small loads a portion of the main field of theexciter is shunted around the armature, thus reducing the field in whichthe armature rotates and cutting down the potential of the exciter forsmall loads. By means of the coils traversed bythe rectifiedcurrent Iincrease the flux through the armature through the agency of therectified current, thus causing the field of the exciter to vary in sucha manner as to cause the potentialof the exciter to practical] y followthe ideal curve.

I will describe my invention more in particular by reference to theaccompanying drawings, in whichgram illustrating generator loads asabscissas and exciter potentials as ordinates, the curve A defining theexciter potential necessary for ideal regulation under changing loads onthe generator, while curve B defines the relation as existingin a simpleseries shunt or coin-- pound dynamo used as an exciter with a rectifiedcurrent-coil but without a shuntingcore. Fig. 6 is a diagramillustrating the distribution of the magnetic field in the modisegmentsof the rectifier.

fication shown in Fig. 4. Fig. 7 is a diagram illustrating the manner ofconnecting the exciter shown in Fig. 2 with the generator. Fig. 8 is asimilar view showing the manner of connecting the exciter shown in Fig.t with the generator.

- Like letters refer to like parts in the several views.

As illustrated in Fig. 1, the generator 0 is provided with a number ofpolar projections c c, in front of which the armature is adapted torotate. Field-coils c o are provided upon the polar projection c andconnected with the brushes of the exciter (Z. The exciter (Z is providedwith a shunt (or series) field winding (1. The armature e of thegenerator is provided with coils c e, the armature-circuit beingconnected with a conductor 6 which extends to a collecting-ring f, uponwhich bears a brush f, connected with one side of the line. Thearmature-circuit is also connected with conductor e which extends to oneside of the rectifying-commutator g, the armature-circuit being thusconnected with the alternate The other segments of the rectifier areconnected by conductor 6 with collecting-ring f upon which bearsthe-brush f connected with the opposite side of the line. Upon therectifier g rest brushes g g which are connected with the field-coils 9provided upon the exciter (Z.

The alternating current generated in the armature passes through therectifier g, whereby the alternating current is transformed into anintermittent direct current. The rectified current then passes throughthe coils g g upon the exciter back to the rectifier g, which convertsthe intermittent direct current into an alternating current, whichpasses to theringf and thenceto the line,

returning to the ring f and passing back to the armature. The currentgenerated by the exciter (1 passes through the field-coils c to maintainthe field excitation of the generator.

field-coils 0 thereby increasing the field ex citation of the generatorto maintain the increased currentoutput. hen the current output isdecreased, the field excitation of -the exciter is correspondinglydiminished,

thus decreasing the exciter potential and thereby decreasing the fieldexcitation of the generator.

If exciter magnetizing force or ampere turns be plotted as abscissas andexciter voltages as ordinates, some such curve as curve B, Fig. 5, willbe obtained, the curve being concave to the axle of abscissas thusindicating that for equal increments of current applied .to the fieldthe potentials increase at a decreasing rate. If a similar curve beplotted to represent the potential of the exciter for the same equalincrements, in order that ideal regulation may result, a curve similarto curve Awillbe obtained. The curve is convex to the axis of abscissas,thus indicating that the potential of the exciter should increase at anincreasing rate instead of a decreasing rate, as actually obtained.

In order to cause the potential of the exciter to follow the curve A itis necessary to reduce the potential of the exciter for small loads andto increase the potential for large loads.

In Figs. 2 and 3 I have illustrated an exciter provided with a shunt (orseries) coil d adapted to excite the field. The pole-pieces d d areslotted or cut away at the middle and auxiliary pole-pieces (Z d areinserted therein, an airspace being left between the two pairs ofpolepieces. The coil g adapted to be traversed by the rectified current,is wound about the core (1 uniting the pole-pieces d (1. The pole-pieces(Z d and the core cl thus form a magnetic shunt about thearmature,through which a portion of the field generated by the mainwinding d is adapted to pass. The coil g is wound to oppose the lines offorce thus shunted, so that as the current through the coil is increaseda greater number of the lines of force are reverted throughthe armature.Thus for small loads a considerable portion of the field is shunted pastthe armature, so that the potential of the exciter falls below thatwhich it would attain were the magnetic shunt absent-that is, if in theabsence of the shunt the potential were that indicated by the point a onthe curve B, Fig. 5, due to the presence of the magnetic shunt thepotential would fall to that indicated by the point a upon the curve A.If theload upon the generator is increased, increased current will flowthrough the coil g which is in series with the load, and a portion ofthe shunted lines of force will be reverted through the armature,thusincreasing the potential of the exciter. Thus while small loads areon the generator the coil g acts to merelyrevert the shunted lines offorce through the armature; but as the load increases the coil g acts topositively direct lines of force through the armature. By thisarrangement I am able to secure practically ideal regulation, the curveof the exciter potential being caused to follow the curve A instead ofthe curve B, as heretofore. Instead of providing slots in the polepieces(Z d for the reception of the pole-pieces d d, the auxiliary pole-piecemay be placed to one side of the main pole-piece or the two sets ofpole-pieces be cast in one piece. In the latter case, due to the absenceof the airspace between the two sets of pole-pieces, it will be founddesirable to place an auxiliary coil (1 (shunt or series) upon themagnetic shunt, which may be adjusted to permit the desired number oflines of force to be shunted past the armature. It may also be founddesirable to employ the auxiliary coil d when the air-spaces arepresent.

In Fig. 4 I have illustrated a modification in which the coil g placedaround the shunt of the magnetic field, is adapted to aid the shuntingof the field around the armature instead of opposing it, as shown inFig. 2. Around the main field is provided a coil g adapted to betraversed by the rectified currents. The main field of the exciter isthus increased as the load increases, due to the coil g but the currentthrough the coil g being likewise increased the number of lines of forceshunted past the armature is also increased. The shunt magnetic circuitis so proportioned that the metal composing it becomes graduallysaturated, so that equal increments of current through the coil g have adecreasing shunting effect upon the lines of force. The field throughthe armature is thus caused to increase at an increasing rate.

In Fig. 6 is illustrated graphically the distribution of the magneticfield of the abovedescribed modification. The curve A is obtained byplotting magnetizing current as abscissas andthe total number ofmagnetic lines in the main exciter field as ordinates, the curve A thusindicating the relation between the total number of magnetic lines inthe main exciter field and the exciting-current. Curve B is obtained byplotting magnetizing current as abscissas and the number of magneticlines in the magnetic shunt as ordinates, curve B thus indicating therelation between the number of magnetic lines in the magnetic shunt andthe exciting-current. The magnetic field in which the armature revolveswill be that produced by the main exciter field reduced by that of themagnetic shunt-that is, the curve C is obtained by subtracting theordinates of the curve B from the ordinates of the curve A, the curve 0thus representing the field in which the armature rotates. It will beobserved that the main exciter field, as shown by the curve A, is soproportioned that it does not produce saturation throughout the entireworking range, while the magnetic shunt, as shown by curve B, is of suchproportion that it reaches saturation at some desired point in itsworking range. The curve C is thus modified, so as to be convex to theaxis of X, which, as shown in connection with Fig. 5, is the curve forideal regulation, the strength of the field through the exciter armaturethus increasing at an increasing rate.

In Fig. 7 I have illustrated the exciter shown in Fig. 2 connected withthe generator, the field-coil d of the exciter being connected either inshunt or in series with the working circuit of the exciter, a shuntconnection being illustrated. The coil 9 is connected in circuit withthe rectifier and is traversed by the rectified currents, the coil gbeing so wound relatively to the coil d, that the two coilsact to directlines of force through the armature in;- the same direction, asindicatedby the arrows. Sincethe working circuit ofthe exciter is ofpractically constant resistance under all loads,the magnetizing power ofthe coil cl gradually increases as the voltage. of the exciterincreases, the main field generated by the coil (1 thus continuouslyincreasing as the voltage of the exciter increases. WVere the excitersubjected to the influence of: the

coil d alone the voltage of the eXciter would increase at-a decreasingrate; but since amagnetic shunt is provided about .the armature aportion of the lines of force that would otherwise pass through thearmature at small loads is diverted through the magnetic shunt encircledby the coil g As thec'urrent in the working circuit of the generatorincreases, the current traversing ;.the coil g increases and opposesthepassageof the diverted lines of force and causes an increase of thenum ber of lines of force passing through the armature. Thetwo coils dand g thus act together to cause the number of linesof force passingthrough the armature and in consequence the voltage of the exciter toincrease at an increasing rate. It will thus be observed that thevoltage of the exciter depends upon three quantities: first, the linesof force generated by the coil cl; second, the lines-of force generatedby the coil g and, third, the

field diverted past the armature and passing through the magnetic shuntencircled by theageof the eXciter increases at an increasing rate.

In Fig. 8 I have illustrated the exciter shown in Fig. 4 connected withthe generator, .the coil (1 being illustrated as connected in shunt withthe working circuit of the exciter and being thus traversed by a currentwhich increases as the voltage of the exciter increases. The coils g and9 adapted to be traversed by the rectified current, are shown asconnected in multiple, though they, may be connected in series, as maybe desired. coil g is wound to assist the coil d, so that the mainmagnetic field generated by the coils (Z and g increases at a decreasingrate, as explained in connection with Fig. 1, and in consequence thevoltage of the exciter would increase at a decreasing rate were it notfor the presence of the magnetic shunt encircled by the coil A portionof the magnetic lines of the main field are thus diverted past thearmature at small loads. The coil g is wound, as indicated by the arrow,to assistv the diversion of the lines of forcepast the ar The mature.The coil g? is most effective in as sisting the diversion of the linesof force at small loads, and as the load increases and the point ofsaturationof the magnetic shunt is approached the'coil g has a less andless effect in diverting the lines of force. past the armature, and inconsequence the number of lines of force passing through the armatureincreases at an increasing rate and the voltage of the exciter increasesat an. increasing rate.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is

1. The combination with an alternating current generator, of acontinuousor direct ourvrent exciter adapted to;energize the field ofsaid generator, a rectifier for rectifying the alternating current ofthe generator, a shunt .magnetic core for said eXciter field coilsprovided upon the exciter adapted to be traversed .by said rectifiedcurrent, said field coils being arranged to coact with the main fieldcoils of the exciterand with said shunt magnetic core to effect thereduetionof the strength of the field for. small loads and the increaseof the strength for larger loads; substantially asdescribed.

2. The combination with an alternating current generator, of a direct orcontinuous current exciter adapted to energize the field there of, arectifier for rectifying the alternating current, a shunt magneticcircuit about the armature of the eXciter, and a field coil providedupon said shunt magnetic circuit adapted to be traversed by therectified current; substantially as described.

3. The combination with an alternating current generator of a direct orcontinuous current exciter, adapted to energize the field thereof, arectifier for rectifying the alternating current, a shunt magneticcircuit provided about the armature of the exciter, a field coil adaptedto be traversed by the rectified current provided upon said shuntmagnetic circuit and wound to oppose the field diverted through theshunt magnetic circuit; substantially as and for the purpose set forth.

4. The method of regulating the potential of an alternating currentgenerator, which consists in energizing the field thereof by means of acontinuous or direct current supplied by an eXciter, rectifying thecurrent produced by the generator, and then through the agency of. saidrectified current variably shunting lines of force around the armature,thereby effecting the reduction of the strength of the field for smallloads and the increase of the strength for larger loads; substantiallyas described.

5. The'method of regulating the potential of .an alternating currentgenerator, which consists in energizing the field of the generator by acontinuous or direct current supplied by an exciter, rectifying thecurrent of the generator, shunting a portion of the mag- IIO netic field0f the exciter around the armature a field through the armature;substantially thereof, to cut down the field 0f the exciter asdescribed. 10 for small loads, and subjecting the magnetic In Witnesswhereof I hereunto subscribe shunt t0 the influence of said rectifiedeurmy name this 2d day of April, A. D. 1895.

5 rent to revert the shunted lines of force FRANCIS P. IDE.

through the armature as the current output Vitnesses: of the generatorincreases, and finally to as- HORACE B. \VALMSLEY, sist the field coilsof the exciter in producing ROY W. IDE.

